Boston Power has been working on its electric car battery tech for over a year, after announcing that it would be providing its lithium ion batteries for the Saab 9-3 ePower project. But on Wednesday Boston Power took the wraps off some details about its EV battery tech, and it says it expects other partners (beyond Saab) to deploy the electric car battery tech later this year and in 2012.

Boston Power is selling what it’s calling its Swing Key block of EV batteries, which is basically several of Boston Power’s lithium ion Swing batteries grouped together with a casing and a management and cooling system (see photo). Boston Power says these blocks are the “building blocks” for automakers to build electric cars and that they can provide the same functionality of a large format battery but with the pricing and performance advantages that are being delivered via small-format lithium ion batteries.

Boston Power is offering two types of these Swing Key blocks — a 3.7V, 30 Ah and a 3.7V, 35 Ah — which will be available as samples to automakers by the fall of this year. Boston Power says its batteries provide 50 percent more usable energy density by volume compared to competitors, have a 10-year lifespan and can operate at a wide-ranging temperature, down to -40?C.

To date, Boston Power hasn’t exactly been hitting a home run with its EV battery tech, though it’s still in the early phases. Its first partner, Saab, is a struggling loss-making brand now working with specialty car maker Spyker and continues to have problems. Boston Power has also said there are other car partners in the works for over a year, but it still hasn’t named any. At the same time the Department of Energy rejected a request by Boston Power for $100 million from the advanced battery program to manufacture EV batteries in the U.S., while competitors like A123 Systems did secure funds from that program.

The EV battery market has also been moving more slowly than anticipated, according to battery makers Ener1 and Johnson Controls. Despite scoring several high profile EV battery deals, A123 Systems isn’t making much money off the EV battery market yet, either.